Each year
endometriosis awareness month seems to get bigger and bigger. I would highly
recommend checking out the hashtag #endometriosis if you’re on Twitter to keep
up with all the news and events from around the world.
For this
week’s blog post I’m going to be putting some ideas out there about the origin
of endometriosis. Not the way in which the disease originates in the body
(there could be a whole book written on that subject), but where and when
endometriosis actually came from in the history of humanity.
Some people
tend to think of endometriosis as ‘modern’ condition, however there are several
great resources examining the history of endometriosis, for example Dr Nezhat’s paper
and Dr Redwine’s book, which
suggest that endometriosis has been known about for thousands of years under
different names and guises. But this week I’m going even further back, to the
beginning.
With that in
mind let’s start at the beginning, which is always a good place to start. In
order to find the origin of endometriosis I started by searching for which
animals are known to develop endo spontaneously (there are numerous animals
that can be induced to have ‘experimental endometriosis’ but I’m only
interested in animals in which endo has been found to occur naturally). Having
a thorough search through the literature I discovered endo has been documented
in the following animals (see the end of the blogpost for the references).
Human
(obviously) Rhesus Macaque
Gorilla Cynomolgus
monkey
Olive Baboon Taiwan Macaque
Yellow
Baboon Pigtail Macaque
Hamandryas
Baboon Debrazza’s monkey
Guinea
Baboon African Green
monkey
Dog Face
Baboon Gray-cheeked mangabey
Mandrill White-tufted-ear
marmoset
One
interesting thing you may notice straight away is that all the species noted above
are primates. Endometriosis has never been documented as occurring in any
non-primate species (there is a condition affecting livestock called
endometriosis, but I won’t be counting that as it refers to degeneration of the
endometrium, not the same thing as
the real endometriosis). This tells us there is something these animals have in
common, not shared by other animals that allows them to develop endometriosis. Given
that the majority of these cases of endometriosis in primates have been discovered by accident
or when performing autopsies on the animals, it is highly likely that there are
other primate species in which endo is yet to be discovered (chimpanzee’s, our
closest relatives, are conspicuously absent from the list, for example).
What can we
do then with the above information? To answer that lets look at how all those
species listed above relate to one another. We know from 150 years of
evolutionary biology that all living creatures on earth are related to one
another in a fantastically complex tree of life of which we are only a tiny
branch.
http://www.utexas.edu/features/graphics/2008/tree/tree3.jpg |
(for a more
detailed look at our place in the tree of life, see here http://www.zo.utexas.edu/faculty/antisense/tree.pdf)
Zooming in
on the part of that tree that contains the primates we can see our relation to
those animals closest to us.
Click to enlarge |
Believe it
or not, this is a simplified version of the primate family tree, there are
numerous species that I’ve left out because they’re extinct and I’ve omitted several
species and grouped together others to keep it as simple as I can whilst retaining
the important information. Now if we connect all the species in which endo has
been found, we can see something very interesting.
Click to enlarge |
The red
lines connect all the species in which endometriosis has been documented thus
far, so now we see the natural history of endometriosis. The arrow near the
bottom shows the point at which, from the evidence we have, it is plausible to suggest
endometriosis originated. Whatever long extinct animal lived at this point, it
passed on the predisposition to endometriosis to its relatives. What that predisposition
was exactly remains to be clarified. It must be a genetic predisposition, but
knowing exactly what gene or genes are responsible we cannot say. Mostly
because there is little agreement as to what genes are associated with endo in
humans, let alone across the boundary of species. Whatever it was it changed
something, perhaps the way in which the reproductive system developed, perhaps
the way in which the reproductive organs function, at the moment we can’t say.
If we
suppose that endometriosis did originate at this point, we can now theorise as
to when endometriosis arose by
finding when the species it originated in lived. Looking at where all the red
lines converge we can see it is at the point in time when the group of primates
containing the marmosets (called the New World Primates) split from the group
of primates containing humans, chimps, macaques etc (called the Old World
Primates). The common relative of these groups is thought to have lived in
north Africa near Egypt 1,2, as this is where the highest proportion
of such fossils are found. Analysis of the age of these fossils put them at
around 33-35 million years old 2. However, using genetic analysis to
date species separation based on how closely related they are puts the date at
around 43 million years ago 3. From this evidence we can tentatively
theorise that endometriosis could be tens of millions of years old; older than
human history records, older than humanity itself.
We tend to
think of endometriosis in terms of human history and why shouldn’t we?
Endometriosis affects us in the here and now, but if we consider our past it
may give us hints to the answers we’ve been looking for. For example, if we
know what animals can develop endo and which ones cannot, then perhaps we
should find out why that is. What is it about these animals that make them
different? By answering this question we could finally understand what
predisposes an individual to endo and maybe even how to stop it.
11.
Fleagle J. Primate
adaptation and evolution 2nd Edition (Academic Press, San Diego, 1999)
22.
Kappelman J, Simons E, Swisher C. New age
determinations for the Eocene-Oligocene boundary sediments in the Fayum
depression, northern Egypt. J Geol,
100, 647-668 (1992)
33.
Steiper ME, Young NM. Primate molecular
divergence dates. Mol Phylogenet Evol,
41(2), 384-394 (2006).
References for cases of primate
endometriosis
Gorilla: Doré M, Lagacé A. Spontaneous External
Endometriosis in a Gorilla (Gorilla gorilla). Can Vet J, 26(11), 347-349 (1985)
Olive baboon and Yellow baboon: D'Hooghe
TM, Bambra CS, De Jonge I, Lauweryns JM, Raeymaekers BM, Koninckx PR. The
effect of pregnancy on endometriosis in baboons (Papio anubis, Papio
cynocephalus). Archives of gynecology and
obstetrics, 261(1), 15-19 (1997).
D'Hooghe
TM, Bambra CS, Raeymaekers BM, Koninckx PR. Serial laparoscopies over 30 months
show that endometriosis in captive baboons (Papio anubis, Papio cynocephalus)
is a progressive disease. Fertility and
sterility, 65(3), 645-649 (1996)
Hamadryas baboon: Shalev M,
Ciurea D, Deligdisch L. Endometriosis and stromal tumor in a baboon (Papio
hamadryas). Laboratory animal science,
42(2), 204-208 (1992).
Guinea baboon: Dallwig RK, Langan JN, Hatch DA, Terio
KA, Demitros C. Bilateral hydronephrosis secondary to endometriosis managed by
endoscopic ureteral stent placement in a captive Guinea baboon (Papio papio). J Zoo Wildl Med, 42(4), 747-750 (2011).
Dog face baboon: Folse DS,
Stout LC. Endometriosis in a baboon (Papio doguera). Laboratory animal science, 28(2), 217-219 (1978)
Rhesus macaque: Zondervan KT, Weeks DE, Colman R et al. Familial aggregation of
endometriosis in a large pedigree of rhesus macaques. Human reproduction (Oxford, England), 19(2), 448-455 (2004)
Crab eating
macaque: Fanton
JW, Hubbard GB. Spontaneous endometriosis in a cynomolgus monkey (Macaca
fascicularis). Laboratory animal science,
33(6), 597-599 (1983)
Formosan macaque: Chin S.
Endometriosis and pyometra in a Taiwan rhesus (Macaca cyclopis). J Chin Soc Vet Sci, 20, 58-64
(1994)
Pigtail macaque: DiGiacomo
RF, Hooks JJ, Sulima MP, Gibbs CJ, Jr., Gajdusek DC. Pelvic endometriosis and
simian foamy virus infection in a pigtailed macaque. Journal of the American Veterinary Medical Association, 171(9),
859-861 (1977)
De Brazza’s monkey: Binhazim
AA, Tarara RP, Suleman MA. Spontaneous external endometriosis in a De Brazza's
monkey. J Comp Pathol, 101(4),
471-474 (1989)
African
green monkey: Cary C, Peter G, Schiffer S. A case report and review of endometriosis
in nonhuman primates. Laboratory animal
science, 32, 426 (1982)
Magabey: Schmidt R, Hartfiel D. Endometriosis in
a Gray-Cheeked Mangaby [Cercocebus albigena]. J Zoo An Med, 9(2), 42-45 (1978).
Mandrill: Pirarat N, Kesdangsakolwut S,
Chotiapisitkul S, Assarasakorn S. Spontaneous diabetes mellitus in captive
Mandrillus sphinx monkeys: a case report. J
Med Primatol, 37(3), 162-165 (2008).
Nakamura S,
Ochiai K, Ochi A, Ito M, Kamiya T, Yamamoto H. Spontaneous Endometriosis in a
Mandrill (Mandrillus sphinx). J Comp
Pathol).
Marmoset: Spontaneous pathology of the common
marmoset (Callithrix jacchus) and tamarins (Saguinus oedipus, Saguinus mystax).
J Med Primatol, 38(5), 347-359
(2009).
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